Fusobacteriaceae

Fusobacteriaceae is a family of Gram-negative, non-spore-forming bacteria in the order Fusobacteriales. The best-known member is the genus Fusobacterium, and members are typically slender, spindle-shaped rods that occur singly or in short chains. They are generally anaerobic or facultatively anaerobic and are characterized by their nonmotile, pleomorphic cells.

Ecology and morphology: Organisms in this family are commonly found as part of the normal microbiota of the human oral cavity and gastrointestinal tract and can inhabit other mucosal surfaces. They are often isolated from dental plaque and periodontal pockets and tend to thrive in anaerobic niches.

Clinical significance: Fusobacteriaceae species are mostly opportunistic pathogens. They can be involved in odontogenic and deep soft tissue infections, intra-abdominal infections, liver and brain abscesses, and bacteremia, particularly in settings of underlying disease or breached mucosal barriers. Fusobacterium necrophorum is notable for causing Lemierre’s syndrome, a septic thrombophlebitis of the internal jugular vein following oropharyngeal infection. Some members, such as Fusobacterium nucleatum, have been associated with periodontal disease and have been detected in associations with adverse pregnancy outcomes and colorectal cancer, though causal links remain under investigation.

Laboratory identification and treatment: Fusobacteriaceae are obligate anaerobes and require appropriate culture conditions for growth. Identification increasingly relies on MALDI-TOF mass spectrometry and 16S rRNA sequencing. Management typically involves antibiotics with anaerobic activity; metronidazole or beta-lactam–beta-lactamase inhibitor combinations are commonly used, often with consideration of local susceptibility patterns.